Just to update anyone that is interested... This project is not dead, but life took over and 2 years passed. I had some issue with the 3D and lost my latest revisions, so will have to revisit the design. After re-reading this entire thread again I have some changes I'd like to make. I will post any ...

Thanks for the welcome back. So here is where I am at the moment. As recommended many moons ago I have added a large washer to secure the rubber face seal to the front of the piston. As before this is attached with an M10 screw. Pressed into the rubber face seal is a sleeve to allow the screw to cla...